1. Field of the Invention
The present invention relates to a chemical filter for removing chemical contaminants contained in an air supplied into a clean space and a fan filter unit having the same. More particularly, the present invention relates to a chemical filter for removing chemical contaminants contained in an air supplied into a clean room in which semiconductor device manufacturing processes are carried out, and a fan filter unit having the chemical filter.
2. Description of the Related Art
Semiconductor devices are generally manufactured through several manufacturing processes such as a fabrication process, an electrical die sorting (EDS) process, a packaging process, etc.
In the fabrication process, electronic circuits may be formed on a semiconductor substrate such as a silicon wafer. The EDS process may be carried out for inspecting electrical characteristics of elements and/or semiconductor devices formed on the semiconductor substrate. In the packaging process, the semiconductor devices are separated and packaged with epoxy resin.
In the fabrication process, there are carried out several processes such as a deposition process for forming a layer on the semiconductor substrate, a chemical mechanical polishing (CMP) process for planarizing an upper face of the layer, a photo process for forming a photoresist pattern on the layer, an etching process for forming an electrical pattern using the photoresist pattern, an ion implantation process for implanting predetermined impurities into predetermined portions of the semiconductor substrate, a cleaning process for removing particles from the semiconductor substrate, an inspection process for inspecting defects of the semiconductor substrate on which the layer or the pattern is formed, and/or other processes.
The semiconductor device manufacturing processes are usually performed in a clean space, such as a clean room. A fan filter unit filters continuously supplies a clean air into the clean room in the semiconductor device manufacturing processes. An exemplary conventional fan filter unit for the clean room system is disclosed in U.S. Pat. No. 6,368,393 issued to Hironaka.
FIG. 1 is a schematic cross-sectional view showing a configuration of a conventional clean room system equipped with fan filter units, and FIG. 2 is a schematic cross-sectional view showing a structure of a conventional fan filter unit.
Referring to FIG. 1, a clean room system 10 includes a clean room 12, a ceiling chamber 14 defining an upper boundary of an interior of a clean chamber 12, fan filter units 100 arranged in a matrix shape on a ceiling surface of the clean room 12, an underfloor region 16 (or a utility zone) defined under the clean room 12 by floor panels, an air circulation path 18 for connecting the underfloor region 16 with the ceiling chamber 14, and a cooling coil 20 for controlling a temperature of an air circulated through the air circulation path 18.
A clean air supplied into the interior of the clean room 12 by the fan filter units 100 is exhausted to the underfloor region 16, and then is circulated through the air circulation path 18 and the ceiling chamber 14.
Referring to FIG. 2, each of the fan filter units 100 includes a fan 110 for sucking the air from an interior of the ceiling chamber 14, a chemical filter 120 for removing chemical contaminants, such as ammonia (NH3) and ozone (O3), from the air sucked by the fan 110, and a particle filter 130 for removing particles, such as dusts and moisture, from the air chemically filtered by the chemical filter 120.
The chemical filter 120 is disposed between the fan 110 and the particle filter 130 as shown in FIG. 2. This general construction is of the fan filter unit 100 is also disclosed in the above U.S. Pat. No. 6,368,393.
A lifetime of the chemical filter 120 may be dominated by a velocity distribution of the air passing through a filter medium of the chemical filter 120. Because the velocity distribution of the air sucked into a housing of the fan filter unit 100 may varies according to different localities, a utility efficiency of the chemical filter 120 may be deteriorated. Particularly, a velocity of the air passing through an edge portion of the chemical filter 120 is substantially higher than that a central portion of the chemical filter 120 due to the structure of the chemical filter 120, and the lifetime of the chemical filter 120 is effected by the velocity of the air passing through the edge portion of the chemical filter 120. That is, because an air flow rate in the edge portion is greater than that in the central portion, an adsorption rate of the edge portion is substantially higher than that of the central portion so that a contaminant removal efficiency may be deteriorated in the edge portion. Consequently, the lifetime of the chemical filter 120 is dominated by the velocity distribution and the velocity deviation of the air passing through the chemical filter 120 contrary to the particle filter 130.
Thus, there is a need therefore for an improved fan filter unit that allows a uniform velocity distribution of the air passing through the chemical filter.
Exemplary fan filter units are disclosed in the Japanese Laid Open Patent Publication No. 1999-90143 as shown in FIGS. 3 and 4.
FIG. 3 is a schematic cross-sectional view showing a construction of another conventional fan filter unit, and FIG. 4 is a schematic cross-sectional view showing a construction of still another conventional fan filter unit.
Referring to FIG. 3, a fan filter unit 200 includes a chemical filter 210 for removing chemical contaminants contained in an air of an interior of a ceiling chamber, a particle filter 230 for removing particles from the air chemically filtered by the chemical filter 210, and a fan 220 disposed between the chemical filter 210 and the particle filter 230. A buffer space 240 is provided between the chemical filter 210 and the fan 220 so as to improve a velocity distribution of the air passing through the chemical filter 210.
However, in the fan filter units 100 and 200 as shown in FIGS. 2 and 3, when replacing the chemical filter 120 or 210, the fan filter unit 100 or 200 should be completely dismantled, and consequently time required for replacement work is increased. In addition, the time required may be increased because it is not ease to secure a sufficient working space, and a downtime of the clean room system may be increased because operation of the fan 110 or 220 is interrupted during a replacement work.
Referring to FIG. 4, a chemical filter 310 having a rectangle box shape is connected to an inlet 322 of a fan 320, and a particle filter 330 is connected to an outlet of the fan 320. A fan filter unit 300, as shown in FIG. 4, may shorten the time required for a replacement work of the chemical filter 310. However, there is a problem that a velocity distribution of the air passing through the chemical filter 310 is not uniform because an air velocity difference between an upper portion and side portions of the chemical filter 310. Particularly, the air velocity in edge portions of the chemical filter 310 is lower than those of flat portions of the chemical filter 310.